[swift-evolution] Remove nil and NilLiteralConvertible

[Xiaodi Wu]

On Wed, Jun 8, 2016 at 3:52 PM, Brandon Knope <bknope at me.com> wrote:

> .none or a more appropriate keyword like “none” (imo)
>
>
My point is that `.none` exposes the underlying enum. The premise here is
that the enum is an implementation detail. You'll notice that, currently,
significant sugar and magic is devoted to allowing you to work with
optionals without ever writing `.some` or `none`. For example, `if let x =
...` and friends allow you to avoid writing `if case .some(let x) = ...`,
while you can write `return x` instead of `return .some(x)`. This was,
IIUC, a deliberate choice to allow progressive disclosure of the language
to learners. Renaming `nil` to `none` is a different proposal from Anton is
proposing here.


> Brandon
>
> On Jun 8, 2016, at 4:47 PM, Xiaodi Wu via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> It's been pointed out before that Optional being an enum type is treated
> like an implementation detail. Currently, it is possible to teach the
> concept of Optional without introducing enum types or generics. How would
> you do so after elimination of nil?
>
>
> On Wed, Jun 8, 2016 at 3:41 PM, Антон Жилин <swift-evolution at swift.org>
> wrote:
>
>> (No joking)
>> Points:
>>
>> 1. When nil was added to the language, we could not infer enumeration
>> type:
>> if x != Optional.none { ... }
>>
>> Now it looks like this:
>> if x != .none { ... }
>>
>> If at this point we had a proposal to add nil as a replacement for .none,
>> would we accept it?
>>
>> 2. nil is very generic, it only approximately allows to express the
>> intentions.
>> In case of Optional, .none is clearer. In case of JSON processing, .null
>> is clearer. In case of a semantically nullable struct,
>> NilLiteralConvertible usually goes to default constructor.
>>
>> 3. Too many "empty" things: .none, nil; NSNull, Void, NoReturn types.
>>
>> 4. There should be a single consistent terminology: no value in Swift
>> equals none.
>>
>> - Anton
>>
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160608/dcb69736/attachment.html>